JP3871219B2 - Method for producing anisotropic magnet powder - Google Patents

Description

つまり、水素は、ＲＦｅＢ系合金の格子間あるいは結晶粒界に侵入するだけであり、本工程中では基本的に相変態を生じない。
【００３５】
原料合金の組成にもよるが、通常、８７３〜１０３３Ｋで水素化・不均化反応を生じ始めるところ、本工程中の温度を前記８７３Ｋを超えて設定すれば、部分的に組織変態を起して組織が不均一となる。これは、異方性磁石粉末の磁気特性を著しく低下させる要因となり好ましくない。従って、本工程は８７３Ｋ以下の温度、より望ましくは７２３Ｋ以下、さらにいえば、室温〜５７３Ｋ程度の温度域で行われれると良い。低温水素化工程中の水素圧力（分圧）は特に拘らないが、例えば、３０〜１００ｋＰａとすると好適である。水素圧力を３０ｋＰａ以上とすることでＲＦｅＢ系合金への水素吸蔵に要する時間を短縮でき、１００ｋＰａ以内とすることで経済的に水素吸蔵を行い得る。なお、処理雰囲気は、水素ガスのみならず、例えば、水素ガスと不活性ガスとの混合ガス等で構成されても良い。重要なのは水素分圧であり、これは以下の工程でも同様である。
【００３６】
<2>高温水素化工程
高温水素化工程は、ＲＦｅＢ系合金を水素分力が１０〜１００ｋＰａで温度が９５３〜１１３３Ｋ内の第１処理温度（Ｔ１）である処理雰囲気に保持する工程である。本工程で、水素を吸蔵したＲＦｅＢ系合金の組織は、本工程により三相分解（Ｆｅ相、ＲＨ₂相、Ｆｅ₂Ｂ相）される。この際、次の水素化・不均化反応が主に生じていると考えられる。
【化２】

すなわち、先ず、水素を吸蔵したＲＦｅＢ系合金は、ＦｅとＲの水素化物（ＲＨ₂）に分解されて層状のラメラ組織を形成する。このＦｅはＢを過飽和に固溶させた状態にあると考えられる。そして、そのラメラ組織は、一方向にのみ歪みが導入されたものとなっており、この歪みに沿った形で、Ｆｅ中に過飽和に固溶していたBが正方晶のＦｅ₂Ｂとして一方向に析出すると考えられる。
【００３７】
ここで、上記反応速度が大きいと、歪みが一方向に配向したラメラ組織は形成されず、析出してくるＦｅ₂Ｂの方位もランダムとなってしまう。つまり、異方化率が低下してＢｒも低下する。従って、高磁気特性の異方性磁石粉末を得るには、上記反応をできる限り緩やかに進行させることが好ましい。この反応速度を緩やかに行うために、本工程では水素分圧の上限を１００ｋＰａに抑制している。但し、水素分圧があまりにも小さいと、反応が起らなかったり、多量の未変態組織が残存して保磁力の低下を招くため好ましくないので、その下限を１０ｋＰａとした。
【００３８】
また、本工程中の処理温度が９５３Ｋ未満では上記反応が進行せず、それが１１３３Ｋを超えると過飽和ＦｅからＦｅ₂Ｂが一方向に析出しにくくなったり、反応速度が速いために前記ラメラ組織が形成されにくくなって、結局、磁石粉末のＢｒの低下を招くようになる。そこで、本工程は、上記反応が緩やかに進行する９５３〜１１３３Ｋ中の第１設定温度（Ｔ１）で行うこととした。なお、好ましい反応速度等の詳細は、前述した特許文献５や非特許文献１にも記載されている。
【００３９】
<3>組織安定化工程
組織安定化工程は、高温水素化工程末期の反応速度を上昇させてその反応を十分に完了させ、上記三相分解を確実に行わせるものである。このため、組織安定化工程では、処理温度（Ｔ２）または水素分圧（Ｐ２）を適宜選択して、高温水素化工程末期の反応速度を上昇させる処理雰囲気が形成されれば良い。具体的には、高温水素化工程中の処理温度（Ｔ１）や水素分圧（Ｐ１）と比較して、少なくとも、Ｔ２＞Ｔ１またはＰ２＞Ｐ１であれば足る。但し、組織安定化工程のＰ２やＴ２を、高温水素化工程のＰ１やＴ１よりも高くすることが目的ではなく、高温水素化工程末期の反応速度を向上させることが目的である。従って、その反応速度が高まる限りにおいて、Ｔ２＞Ｔ１かつＰ２＜Ｐ１でも良いし、Ｔ２＜Ｔ１かつＰ２＞Ｐ１でも良い。例えば、Ｐ１が３０ｋＰａであったときに、Ｐ２を２０ｋＰａにしたとしても、Ｐ２＜Ｐ１の影響を打ち消す以上にＴ２をＴ１よりも十分に上昇させれば、組織安定化工程の目的は十分に達成される。逆に、例えば、Ｔ１が１０７３Ｋであったときに、Ｔ２を１０４８Ｋにしたとしても、Ｔ２＜Ｔ１の影響を打ち消す以上にＰ２をＰ１よりも十分に上昇させれば、組織安定化工程の目的は十分に達成される。
【００４０】
勿論、高温水素化工程から組織安定化工程へスムーズに移行させ、磁気特性の高い磁石粉末を安定的に得る上で、組織安定化工程の処理雰囲気は、Ｔ２＞Ｔ１かつＰ２≧Ｐ１またはＰ２＞Ｐ１かつＴ２≧Ｔ１の条件を満たす方がより良い。すなわち、高温水素化工程を基準にした場合に、組織安定化工程の処理温度または水素分圧の少なくとも一方が、高温水素化工程のそれらより高いことを意味する。この条件により、反応が進行してその反応速度の低下した水素化・不均化反応をさらに促進させ得る。そして、高温水素化工程後の残存した２−１４−１相や水素化分解すべき析出物の水素化分解が速やかに進行する。
【００４１】
ここで、昇温過程や昇圧過程中に水素化分解が完了する場合もあるが、いずれにしても、組織安定化工程下で水素化分解がほぼ完全に完了するまで保持するのが好ましい。
【００４２】
組織安定化工程は、前処理である高温水素化工程で残存した２−１４−１相や水素化分解すべき析出物を水素化分解するために行われる。この点を考慮して、水素分圧Ｐ２の範囲は１０ｋＰａ以上、処理温度Ｔ２の範囲は１０３３〜１２１３Ｋとした。
【００４３】
水素分圧が１０ｋＰａ未満では、再結合が開始され、その結果、磁気特性が低下する。一方、その上限は特に制限がない。むしろ、Ｐ２が高い程、組織安定化工程の効果が高まる傾向にある。但し、処理炉のコストや耐久性等の生産上の都合を考えると、Ｐ２の上限は２００ｋＰａが好ましい。
【００４４】
処理温度を１０３３〜１２１３Ｋとしたのは、１０３３Ｋ以下では、残存した２−１４−１相や水素化分解すべき析出物の水素化分解が進行せず、磁気特性の低下を招く。一方、上限を１２１３Ｋとしたのは、組織の劣化が起こり、磁気特性の低下を招くからである。
【００４５】
<4>制御排気工程
制御排気工程は、組織安定化工程後のＲＦｅＢ系合金を水素分圧が０．１〜１０ｋＰａ中の第３処理圧力（Ｐ３）で温度が１０３３〜１２１３Ｋ中の第３処理温度（Ｔ３）である処理雰囲気に保持する工程である。
【００４６】
本工程で、前工程である高温水素化工程で生成された三相分解中のＲＨ₂相から水素が除去され、Ｆｅ₂Ｂを核として結晶方位の揃ったＲ₂Ｆｅ₁₄Ｂ₁相が再結合される。この際、次の再結合反応が主に生じていると考えられる。
【化３】

この再結合反応も、できる限りゆっくりと進行するのが好ましい。反応速度が速いと、Ｆｅ₂Ｂを核とした結晶方位にゆれが生じて、再結合したＲ₂Ｆｅ₁₄Ｂ₁相の異方性も低くなり、磁気特性が低下するからである。
【００４７】
そこで、本工程では、第３処理圧力（Ｐ３）を０．１〜１０ｋＰａとした。水素分圧を０．１ｋＰａ未満とするような急激な排気を行うと、排気口に近い場所の合金材料と遠い場所の合金材料とで排気速度が変わり、再結合反応速度が不均一になり易い。また、この再結合反応は吸熱反応であるため、場所による温度の不均一をも招くことになり、相乗的に、異方性磁石粉末全体の磁気特性低下につながる。一方、水素分圧が１０ｋＰａを超えると、再結合反応が進まず、逆組織変態が不十分となって、高ｉＨｃの異方性磁石粉末が得られなくなる。
【００４８】
また、本工程中の処理温度が１０３３Ｋ未満では上記反応が進行せず、一方、１２１３Ｋを超えると再結合反応が適切に進行せず、結晶粒の粗大化等によって高ｉＨｃの異方性磁石粉末が得られなくなる。そこで、本工程は、上記反応が緩やかに進行する１０３３〜１２１３Ｋ中の第３処理温度（Ｔ３）で行うこととした。なお、この場合の好ましい反応速度等の詳細も、前述した特許文献５や非特許文献１にも記載されている。
【００４９】
<5>強制排気工程
強制排気工程は、制御排気工程後のＲＦｅＢ系合金（ＲＦｅＢＨｘ）から残留した水素（残留水素）を除去する工程である。この際、次の反応が主に生じていると考えられる。
【化４】

本工程中の処理温度や真空度等は特に限定されないが、上記Ｔ３と同程度かそれより低い温度で、１Pa以下まで真空引きするのが好ましい。真空度が弱いと、水素が残存するおそれがあり、磁気特性の低下につながるからである。また、処理温度が低すぎると排気に長時間を要し、高すぎると結晶粒の粗大化を招き好ましくない。
【００５０】
ところで、この強制排気工程は、上記制御排気工程と連続的に行う必要はない。前記制御排気工程後、本工程前に、合金材料を冷却する冷却工程を入れても良い。冷却工程を設けると、例えば、制御排気工程後に得られたＲＦｅＢ系合金を別の処理炉等に移して、量産時に強制排気工程等をバッチ処理する場合などに有効である。そのＲＦｅＢ系合金を所定粒度に粉砕等する際にも、冷却工程を設けると好都合である。また、後述の拡散熱処理を行う場合、この冷却工程を入れることで、ＲＦｅＢ系合金（Ｒ２Ｆｅ１４Ｂ１Ｈｘ）と拡散材料との混合が容易となる。なお、この場合の拡散熱処理工程は、本発明でいう強制排気工程を兼ねるものと考えても良い。すなわち、強制排気工程の一形態が拡散熱処理工程であると考えても良い。
【００５１】
冷却工程は、ＲＦｅＢ系合金の冷却状態を問題とするものではなく、その取扱いを容易とするためであるから、冷却温度、冷却方法、冷却雰囲気等を問わない。また、水素化物は耐酸化性があることから、そのＲＦｅＢ系合金を室温で大気中に取出すこともできる。なお、当然に、冷却工程後には、ＲＦｅＢ系合金（Ｒ２Ｆｅ１４Ｂ１Ｈｘ）を再び昇温し真空引きする等の強制排気工程を行うのが良い。
【００５２】
また、制御排気工程後のＲＦｅＢ系合金（Ｒ２Ｆｅ１４Ｂ１Ｈｘ）に拡散材料を混合し、その後、拡散熱処理工程を行う場合、その工程後に強制排気工程を一括して行えば効率的である。
【００５３】
（３）拡散熱処理
上記ｄ−ＨＤＤＲ処理のみでも、十分に高磁気特性の異方性磁石粉末は得られる。しかし、以下説明する拡散熱処理を行うことで、保磁力、さらには耐食性の向上した異方性磁石粉末を得ることができる。
【００５４】
この拡散熱処理は、基本的に、制御排気工程後のＲＦｅＢ系合金（Ｒ２Ｆｅ１４Ｂ１Ｈｘ）または強制排気工程後のＲＦｅＢ系合金（異方性磁石粉末）に、Ｄｙ等からなる拡散材料を混合して混合粉末とする混合工程と、その混合粉末を加熱してＲＦｅＢ系合金の表面および内部にＤｙ等を拡散させる拡散熱処理工程とからなる。
【００５５】
<1>拡散材料
拡散材料は、ジスプロシウム（Ｄｙ）、テルビウム（Ｔｂ）、ネオジム（Ｎｄ）、プラセオジム（Ｐｒ）またはランタン（Ｌａ）からなる元素（以下、「Ｒ１」という。）を少なくとも一種以上含有するものであれば良い。例えば、Ｄｙ、Ｔｂ、Ｎｄ、ＰｒおよびＬａからなる元素（Ｒ１）の単体、合金、化合物または水素化物（Ｒ１材料）の１種以上を含むものである。その水素化物には、Ｒ１の単体、合金または化合物の水素化物がある。更には、これらの混合物であってもよい。混合工程前の拡散材料の形態は問わないが、混合工程により混合粉末となり易いものが好ましい。そこで必要に応じて粉末状の拡散材料（拡散粉末）を用いるのが良く、Ｒ１のＲＦｅＢ系合金への均一な拡散も図り易い。
【００５６】
Ｒ１材料は、３ｄ遷移元素および４ｄ遷移元素の１種以上の遷移元素（以下、「ＴＭ」という。）を含み、拡散熱処理工程でＲ１と共にＴＭがＲＦｅＢ系合金の表面および内部に均一に拡散するとより好適である。これにより、さらなる保磁力の向上や永久減磁率の低下を図ることができる。なお、３ｄ遷移元素は、原子番号２１（Ｓｃ）〜原子番号２９（Ｃｕ）であり、４ｄ遷移元素は、原子番号３９（Ｙ）〜原子番号４７（Ａｇ）である。特に、８族のＦｅ、Ｃｏ、Ｎｉが磁気特性の向上を図る上で有効である。また、拡散材料は、Ｒ１材料の粉末と、ＴＭの単体、合金、化合物または水素化物（ＴＭ材料）の粉末とを別々に用意しておきこれらを混合したものでも良い。なお、本明細書でいう化合物には、金属間化合物も含む。また、水素化物には、水素を固溶状態で含んでいるものも含まれる。
【００５７】
このような拡散材料は、例えば、ジスプロシウム粉末、ジスプロシウムコバルト粉末、ジスプロシウム鉄粉末、ジスプロシウム水素化物粉末またはジスプロシウムコバルト水素化物粉末、ジスプロシウム鉄水素化物粉末である。特に、Ｒ１がＤｙであると、異方性磁石粉末の保磁力が向上し、また、ＴＭがＣｏであると、異方性磁石粉末のキュリー点が向上する。さらに、ＴＭにＦｅが含まれると低コスト化を図れる。
【００５８】
特に、拡散材料は、平均粒径が０．１〜５００μｍの拡散粉末であるとＲ１の拡散を図り易く好ましい。平均粒径が０．１μｍ未満の拡散粉末は製造が困難でり、平均粒径が５００μｍを超えると、ＲＦｅＢ系合金との均一な混合が困難となる。そして、その平均粒径が１〜５０μｍであるとより好ましい。
【００５９】
このような拡散粉末は、Ｒ１材料を一般的な水素粉砕や乾式若しくは湿式の機械粉砕（ジョークラッシャ、ディスクミル、ボールミル、振動ミル、ジェットミル等）等して得られる。もっとも、Ｒ１材料の粉砕は水素粉砕が効率的であり、この観点から水素化物粉末を拡散粉末として使用するのが好ましい。さらに、水素粉砕後、乾式若しくは湿式の機械粉砕等を行うのがより好ましい．
【００６０】
<2>拡散熱処理前のＲＦｅＢ系合金
拡散材料を混合するＲＦｅＢ系合金は、制御排気工程後または強制排気工程後に得られたものを使用するのが効率的であり、異方性磁石粉末の磁気特性を図る点からも好ましい。制御排気工程後のＲＦｅＢ系合金（Ｒ２Ｆｅ１４Ｂ１Ｈｘ）を使用した場合、拡散熱処理工程前に脱水素工程を行うか、強制排気工程を兼ねて拡散熱処理工程を行うのが良い。すなわち、前記混合工程は、前記制御排気工程後に得られたＲＦｅＢ系合金の水素化物粉末とＲ１を含む水素化物粉末からなる拡散粉末とを混合して混合粉末とする工程であり、前記拡散熱処理工程は、該混合粉末から残留水素を除去する前記強制排気工程を兼ねた工程であっても良い。
【００６１】
また、ＲＦｅＢ系合金の形態は問わないが、拡散材料との混合性、拡散性等を考慮して、その平均粒度が２００μm以下であると好ましい。
【００６２】
<3>混合工程
混合工程は、上記ＲＦｅＢ系合金と拡散材料とを混合して混合粉末とする工程である。混合工程には、ヘンシェルミキサ、ロッキングミキサ、ボールミル等を用いることができる。また、拡散熱処理工程の炉に混合機能が付与された回転キルン炉や、回転レトルト炉を用いることが特に好ましい。ＲＦｅＢ系合金と拡散材料との均一な混合を行うために、各原材料の粉砕、分級等を適宜行うと良い。分級を行うことで、ボンド磁石等の成形が容易にもなる。また、混合工程は、酸化防止雰囲気（例えば、不活性ガス雰囲気や真空雰囲気）で行うことが、異方性磁石粉末の酸化抑制のために好ましい。
【００６３】
ところで、拡散材料の混合は、混合粉末全体を１００質量％としたときに、拡散材料を０．１〜３．０質量％の割合で行うと好適である。拡散材料の混合割合を適切に調整することで、保磁力、残留磁束密度および角形性のいずれにも優れた高磁気特性を発揮すると共に永久減磁率にも優れた異方性磁石粉末が得られる。
【００６４】
<4>脱水素工程
脱水素工程は、混合粉末中の残留水素を除去する工程である。ここで、ＲＦｅＢ系合金と拡散材料のうちの少なくともひとつが水素化物である場合、その水素を含有するために、拡散熱処理工程前または拡散熱処理工程を兼ねた脱水素工程が必要となる。
【００６５】
強制排気工程前のＲＦｅＢ系合金に拡散材料を混合し拡散熱処理を行った場合、本工程はｄ−ＨＤＤＲ処理の強制排気工程を兼用したものとなる。強制排気工程後のＲＦｅＢ系合金に水素化物からなる拡散材料を混合して拡散熱処理を行う場合、拡散熱処理工程前に別途、脱水素工程を行う必要が生じる。この場合の脱水素工程は、例えば、１Ｐａ以下、１０２３〜１１２３Ｋの真空雰囲気で行えば良い。１Ｐａ以下としたのは、１Ｐａを超えると水素が残留し、異方性磁石粉末の保磁力低下を招くからである。１０２３〜１１２３Ｋとしたのは、１０２３Ｋ未満では残留水素の除去される速度が低く、１１２３Ｋを超えると結晶粒の粗大化を招くからである。
【００６６】
<5>拡散熱処理工程
拡散熱処理工程は、混合工程後に得られた混合粉末を加熱してＲＦｅＢ系合金の表面および内部に拡散材料のＲ１を拡散させる工程である。
【００６７】
Ｒ１は酸素ゲッタとしても機能し、異方性磁石粉末やそれを用いた硬質磁石の酸化を抑制する。従って、磁石が高温環境下で使用される場合でも、酸化による性能劣化が有効に抑制、防止される。そして、磁石粉末の耐熱性が向上するため、その用途も拡大する。
【００６８】
この拡散熱処理工程は、酸化防止雰囲気（例えば、真空雰囲気中）で行うのが良く、処理温度は６７３〜１１７３Ｋ、特に、制御排気工程の温度Ｔ３以下が好ましい。６７３Ｋ未満では、Ｒ１やＴＭの拡散速度が遅くて効率的ではなく、１１７３ＫやＴ３を超えると、結晶粒の粗大化を招き好ましくない。更に、急冷するのが結晶粒粗大化防止のために好ましい。
【００６９】
（４）その他
本発明の製造方法により得られる異方性磁石粉末は、所望形状の焼結磁石やボンド磁石に形成される。特に、その異方性磁石粉末は形状自由度が大きく高温加熱を必要としないボンド磁石に有効である。このボンド磁石は、得られた異方性磁石粉末へ、熱硬化性樹脂、熱可塑性樹脂、カップリング剤または潤滑剤等を添加混錬した後、磁場中で圧縮成形、押出し成形、射出成形等して製造される。
【実施例】
【００７０】
以下、実施例を挙げて本発明について詳細に説明する。
（供試材の製造）
（１）第１実施例
本発明に係るｄ−ＨＤＤＲ処理の効果を確認するために、表１および表２にそれぞれ示す試料Ｎｏ．１〜２６および試料Ｎｏ．Ｃ１〜Ｃ２４の供試材を製造した。この際に使用する原料として、４種類の異なる組成からなるＲＦｅＢ系合金を用意した。これらの各組成を表３に示す。表３の単位はａｔ％で、合金全体を１００ａｔ％として示した。以降では、表３に示した符号Ａ〜Ｄを用いて、各ＲＦｅＢ系合金を合金Ａ、合金Ｂなどのように区別して呼ぶ。
【００７１】
これらの合金Ａ〜Ｄは次のようにして製造した。いずれもの合金も、所望の組成となるように市販の原料を秤量し、それを高周波溶解炉を用いて溶解し、鋳造して１００ｋｇのインゴットを製作した。この合金インゴットに、Ａｒガス雰囲気中で１４１３Ｋｘ４０時間加熱して組織を均質化した（均質化熱処理）。この合金インゴットをさらにジョークラッシャを用いて、平均粒径１０ｍｍ以下に粗粉砕して、それぞれ組成の異なる合金Ａ〜Ｄを得た。なお、合金Ｄは、溶解・鋳造後に均質化熱処理を施さず粗粉砕を施した。
【００７２】
次に、表１および表２に示すように、供試材毎に、使用する合金の種類や工程内容を変えて、多数の供試材を製造した。各供試材の処理量は、いずれも１２．５ｇとした。各供試材毎に使用する合金を処理炉に入れて、室温ｘ１００ｋＰａｘ１時間の共通した低温水素化工程を施した。続いて、１８０分の高温水素化工程を施した。この高温水素化工程の温度（Ｔ１）および水素分圧（Ｐ１）は各供試材毎に表１、２に示した。
【００７３】
なお、表１中の試料Ｎｏ．２６のみ、上記低温水素化工程を施さずに、所定水素圧力中で、室温から所定温度まで昇温し、高温水素化工程を直接施した。また、試料Ｎｏ．２６の場合、合金インゴットは、５〜１０ｍｍ程度のブロックを使用した。
【００７４】
さらに、水素分圧が１ｋＰａの制御排気工程を９０分間施した。この制御排気工程の温度（Ｔ３）は各供試材毎に表１、２に示した。もっとも、試料Ｎｏ．Ｃ１〜Ｃ１６の場合は、高温水素化工程と制御排気工程とを同温度で行ったのでＴ３＝Ｔ１である。最後に、制御排気工程と同温度で処理炉内の水素分圧を１Ｐａ以下とする強制排気工程を３０分間行った。
【００７５】
ところで、試料Ｎｏ．１〜２６の場合、上記の高温水素化工程と制御排気工程との間に組織安定化工程を設けた。組織安定化工程では、処理温度、水素分圧の少なくとも一方を増加させた。これらの工程パターンを図１、２および３に示す。なお、組織安定化工程中の昇温（Ｔ１→Ｔ２）はいずれも５分間で行ったが、その後の保持時間は供試材毎に変えた。その詳細は表１に示した。
【００７６】
さらに、試料Ｎｏ．１〜２６の内、試料Ｎｏ．１９〜２３では、制御排気工程後にＲＦｅＢ系合金の水素化物を冷却炉に移して室温まで冷却する冷却工程を取入れた。そして、この冷却工程後に、再度加熱し真空引きする上記強制排気工程を行った。このときの工程パターンを図４に示す。
【００７７】
試料Ｎｏ．Ｃ１〜Ｃ１６では、上記組織安定化工程を行わず、高温水素化工程から制御排気工程へ直接移行させた。このときの工程パターンを図５に示す。
【００７８】
試料Ｎｏ．Ｃ１７〜Ｃ２２では、上記組織安定化工程を設けたが、高温水素化工程中のＴ１、組織安定化工程中のＴ２、Ｐ２や制御排気工程中のＴ３を本発明でいう好適な範囲外とした。
【００７９】
試料Ｎｏ．Ｃ２３は、上記組織安定化工程を設けずに、制御排気工程開始から５分経過後に、処理炉内の温度をＴ１→Ｔ３へ５分間かけて昇温したものである。試料Ｎｏ．Ｃ２４は、上記組織安定化工程を設けずに、制御排気工程開始から１５分経過後に、処理炉内の温度をＴ１→Ｔ３へ５分間かけて昇温したものである。これらの工程パターンを図６に示す。
【００８０】
（２）第２実施例
上記ｄ−ＨＤＤＲ処理に加えて拡散熱処理を行った場合の効果を確認するために、表４にす試料Ｎｏ．２７〜４７の供試材を製造した。この際に使用する拡散材料の原料として、６種類の異なる組成からなる希土類合金を用意した。それらの各組成を表５に示す。表５の単位はａｔ％で、合金全体を１００ａｔ％として示した。以降では、表５に示した符号ａ〜ｆを用いて、各希土類合金を区別する。
【００８１】
試料Ｎｏ．２７〜４７の製造に際して、先ず、表３に示す合金Ｂ〜Ｄのいずれかに、前述した低温水素化工程、高温水素化工程、組織安定化工程および制御排気工程を施し、冷却工程で室温まで冷却して得たＲＦｅＢ系合金の水素化物粉末（平均粒径：１００μｍ）を用意した。
【００８２】
次に、拡散材料として、希土類合金ａ〜ｆのいずれかの水素化物粉末を用意した。希土類合金ａ〜ｆの水素化物粉末の平均粒径はそれぞれ異なるが、いずれも５〜３０μｍ内に収っていた。
【００８３】
上記両粉末を混合した混合粉末に（混合工程）、拡散熱処理工程を行って、拡散熱処理のなされた試料Ｎｏ．２７〜４７の異方性磁石粉末を得た。このときの工程パターンを図７に示す。
【００８４】
試料Ｎｏ．４４は、拡散材料として上記水素化物に替えて希土類合金ｂの粉末（平均粒径：５μｍ）を使用したものである。
【００８５】
試料Ｎｏ．４０は、制御排気工程のＲＦｅＢ系合金の水素化物粉末に替えて、強制排気工程後の異方性磁石粉末を使用した。つまり、制御排気工程後に冷却工程を行わなず、続けて強制排気工程を行った異方性磁石粉末を使用した。このときの工程パターンを図８に示す。
【００８６】
試料Ｎｏ．４７は、制御排気工程後、一旦冷却し、さらに真空中で加熱することで強制排気工程を施した異方性磁石粉末を使用した。このときの工程パターンを図９に示す。
【００８７】
これら試料Ｎｏ．２７〜４７の製造に際して行ったｄ−ＨＤＤＲ処理および拡散熱処理の各条件は次の通りであり、供試材毎に異なる条件は表４に個別的に示した。つまり、ＲＦｅＢ系合金の処理量：１２．５ｇ、低温水素化工程：室温ｘ１００ｋＰａｘ１時間、高温水素化工程：１０５３Ｋｘ１８０分間、組織安定化工程：５分昇温→１０分間保持、制御排気工程：１１１３Ｋｘ１ｋＰａｘ９０分間、強制排気工程：１１１３Ｋｘ１０Ｐａ以下ｘ３０分間、脱水素・拡散熱処理工程：１０７３Ｋｘ１Ｐａ以下ｘ１時間とした。
【００８８】
（３）第３実施例
上記ｄ−ＨＤＤＲ処理および拡散熱処理の量産時の効果を確認するために、さらに、表６および表７に示す試料Ｎｏ．４８〜５４および試料Ｎｏ．Ｃ２５、Ｃ２６の供試材を製造した。試料Ｎｏ．４８〜５１および試料Ｎｏ．Ｃ２５はｄ−ＨＤＤＲ処理のみであり、試料Ｎｏ．５２〜５４および試料Ｎｏ．Ｃ２６はさらに拡散熱処理を施したものである。使用したＲＦｅＢ系合金はいずれも合金Ｂで、その処理量は１０ｋｇである。また、拡散材料はいずれも希土類合金ｂの水素化物粉末を使用した。この拡散材料を、制御排気工程後のＲＦｅＢ系合金の水素化物に、混合粉末全体に対して１〜３質量％の割合で混合した。その他の各工程の詳細は表６および表７に併せて示した。
【００８９】
（供試材の測定）
得られた各磁石粉末の室温での磁気特性（（ＢＨ）ｍａｘ、ｉＨｃおよびＢｒ）を測定した。測定は、ＶＳＭを使用した。測定用試料としては、先ず、磁石粉末を７５〜１０６μｍの粒径に分級し、その分級した磁石粉末を用いて反磁場係数が０．２になるようにパラフィンで固化・成形した。１．５Ｔの磁場中で配向後４．５Ｔで着磁し、ＶＳＭでその(ＢＨ)ｍａｘ、ｉＨｃおよびＢｒを測定した。
【００９０】
（評価）
（１）ｄ−ＨＤＤＲ処理について
試料Ｎｏ．１〜２６と試料Ｎｏ．Ｃ１〜Ｃ２４を対比すると明らかなように、本発明に係る試料Ｎｏ．１〜２６の場合、高温水素化工程と制御排気工程の間に組織安定化工程を施すことで、全体的に磁気特性が向上している。例えば、同組成の合金Ｂからなる異方性磁石粉末の中で、最大エネルギー積（（ＢＨ）ｍａｘ）が最大のものを観ると、従来の試料Ｎｏ．Ｃ７は３６０（ｋＪ／ｍ³）であるのに対し、試料Ｎｏ．４は３７２（ｋＪ／ｍ³）に向上している。更には、合金Ｃからなる異方性磁石粉末の中で、最大エネルギー積（（ＢＨ）ｍａｘ）が最大のものを観ると、従来の試料Ｎｏ．Ｃ１２は３６０（ｋＪ／ｍ³）であるのに対し、試料Ｎｏ．１９は３８２（ｋＪ／ｍ³）に向上している。以上より、本発明の製造方法により製造された異方性磁石粉末は、従来の製造方法に比べ、優れている。
【００９１】
合金Ｂの場合について説明したが、他の合金からなる異方性磁石粉末の場合も、同組成のもの同士で比較すると同傾向にある。なお、試料Ｎｏ．１９〜２３に関しては、制御排気工程と強制排気工程との間に冷却工程を設けた。この工程順でも、優れた磁気特性が得られ、量産化し易いことも確認できた。
【００９２】
次に、試料Ｎｏ．Ｃ１７〜Ｃ２２から、高温水素化工程と制御排気工程の間に組織安定化工程を設けたとしても、好適な温度範囲、好適な水素分圧範囲から外れていれば、好ましい磁気特性は得られない。
【００９３】
また、温度に関しては、試料Ｎｏ．Ｃ２３およびＣ２４を試料Ｎｏ．４等と比較すれば解るように、昇温を制御排気工程中で行うという不適当な昇温を行った場合、磁気特性の向上が望めなかった。
【００９４】
試料Ｎｏ．１１〜１５または試料Ｎｏ．１９〜２２からわかるように、組織安定化工程中の保持時間を増加させることで、保磁力（ｉＨｃ）を向上させることができた。従って、その保持時間を長くすることで異方性磁石粉末の耐熱性を高めることができる。この傾向は、試料Ｎｏ．１１〜１５と試料Ｎｏ．１９〜２２との比較から、制御排気工程と強制排気工程との間に設ける冷却工程の有無に拘らず観られた。
【００９５】
試料Ｎｏ．１７〜１８から、従来のｄ−ＨＤＤＲ工程のＣ５に比べて、組織安定化工程中の水素分圧（Ｐ２）を上げると、磁気特性が向上することがわかった。但し、本発明者の研究に依ると、Ｐ２をある程度を超えて上げても、磁気特性の向上効果は飽和する傾向にあることがわかっている。量産時の処理炉のコストや耐久性等から考えて、組織安定化工程のＰ２の上限は２００ｋＰａとするのが好ましい。
【００９６】
試料Ｎｏ．２４は、Ｔ２＞Ｔ１かつＰ２＜Ｐ１でも良いことを示す実施例である。本実施例のようにＰ１が３０ｋＰａであったときに、Ｐ２を２０ｋＰａにしたとしても、Ｐ２＜Ｐ１の影響を打ち消す以上にＴ２をＴ１の１０５３Ｋから１１３３Ｋまで十分に上昇させれば、組織安定化工程の目的は十分に達成される。 試料Ｎｏ．２５は、Ｔ２＜Ｔ１かつＰ２＞Ｐ１でも良いことを示す実施例である。本実施例のようにＴ１が１１１３Ｋであったときに、Ｔ２を１１０３Ｋにしたとしても、Ｔ２＜Ｔ１の影響を打ち消す以上にＰ２をＰ１の３０ｋＰａから２００ｋＰａまで十分に上昇させれば、組織安定化工程の目的は十分に達成される。その結果、試料Ｎｏ．２４、２５ともに良好な磁気特性が得られている。
【００９７】
試料Ｎｏ．２６および試料Ｎｏ．Ｃ５を比較すると、両者は合金組成および高温水素化工程の条件は同じであるが、低温水素化工程および組織安定化工程の有無で相違する。両者の比較から、低温水素化工程を施さなくても組織安定化工程を施すことで、（ＢＨ）ｍａｘやｉＨｃの磁気特性を高められることがわかった。
【００９８】
（２）拡散熱処理について
試料Ｎｏ．２７〜４７と試料Ｎｏ．１〜２６とを比較すると、全体的に拡散熱処理によってｉＨｃが増加している。磁石に耐熱性を付与すると言う点では重要である。また、試料Ｎｏ．３３等と試料Ｎｏ．４１〜４３とを比べると、拡散材料は０．５〜１質量％程度が好ましく、それ以上増えると磁気特性が低下した。また、試料Ｎｏ．３３と試料Ｎｏ．４４とを比べると、拡散材料は水素化物でなくても十分に効果があることも解った。
【００９９】
試料Ｎｏ．２７〜２９から、拡散熱処理を行う場合であっても、組織安定化工程中の保持時間を増加させることで、ｉＨｃを高められることがわかった。従って、この場合も、組織安定化工程の保持時間を長くすることで異方性磁石粉末の耐熱性を高められる。勿論、試料Ｎｏ．２９〜３２からわかるように、拡散材料を増加させることでｉＨｃが向上し、異方性磁石粉末の耐熱性を高めることもできる。
【０１００】
（３）量産性について
試料Ｎｏ．４８〜５１は試料Ｎｏ．４をベースにその量産化を図ったものであり、試料Ｎｏ．Ｃ２５は試料Ｎｏ．Ｃ７をベースにその量産化を図ったものである。いずれも、処理量が増加することで磁気特性が多少低下する傾向にあるが、試料Ｎｏ．４６〜４９は試料Ｎｏ．Ｃ２５よりもその傾向が小さかった。具体的には、試料Ｎｏ．Ｃ２５は試料Ｎｏ．Ｃ７に対して（ＢＨ）ｍａｘが４２（ｋＪ／ｍ³）低下したのに対し、例えば、試料Ｎｏ．４８は試料Ｎｏ．４から（ＢＨ）ｍａｘが２０（ｋＪ／ｍ³）しか低下していない。このように、本発明の製造方法は従来の製造方法に対して、量産段階での磁気特性の低下が１／２以下となった。従って、本発明の製造方法は工業的にも非常に有効な製造方法であり、試験室レベルに留まらず、量産しても高磁気特性の異方性磁石粉末が得られる。
【０１０１】
試料Ｎｏ．４８〜５１からわかるように、処理量が増加しても、組織安定化工程中の保持時間を増加させることでｉＨｃが向上し、異方性磁石粉末の耐熱性を高められる。
【０１０２】
拡散熱処理を施した試験片Ｎｏ．５２〜５４および試料Ｎｏ．Ｃ２６についても同様に、組織安定化工程を施すことで、量産時でも高磁気特性の異方性磁石粉末が得られるし、拡散材料を増加させることでｉＨｃが向上して異方性磁石粉末の耐熱性を高められることもわかった。
【０１０３】
【表１】

【０１０４】
【表２】

【０１０５】
【表３】

【０１０６】
【表４】

【０１０７】
【表５】

【０１０８】
【表６】

【０１０９】
【表７】

【図面の簡単な説明】
【０１１０】
【図１】各工程の処理内容を模式的に示した第１工程パターン図である。
【図２】各工程の処理内容を模式的に示した第２工程パターン図である。
【図３】各工程の処理内容を模式的に示した第３工程パターン図である。
【図４】各工程の処理内容を模式的に示した第４工程パターン図である。
【図５】各工程の処理内容を模式的に示した第５工程パターン図である。
【図６】各工程の処理内容を模式的に示した第６工程パターン図である。
【図７】各工程の処理内容を模式的に示した第７工程パターン図である。
【図８】各工程の処理内容を模式的に示した第８工程パターン図である。
【図９】各工程の処理内容を模式的に示した第９工程パターン図である。【Technical field】
[0001]
The present invention relates to a method for producing an anisotropic magnet powder that can provide an anisotropic magnet powder with excellent magnetic properties.
[Background]
[0002]
Magnets are used in many devices around us, such as various motors, but more powerful permanent magnets are required due to recent reductions in size, weight, and efficiency of devices. From this point of view, development of RFeB-based magnets (rare earth magnets) made of rare earth elements (R), boron (B), and iron (Fe) has been actively performed. As a method for producing such a rare earth magnet, there is a melt span method which is a kind of rapid solidification method described in Patent Documents 1 and 2 below. Further, as described in Patent Documents 3 and 4, the HDDR method (hydrogenation-deposition-desorption-recombination) in which a hydrogenation / disproportionation reaction is basically caused by two steps of a hydrogenation step and a dehydrogenation step. ) However, any of these conventional methods can only obtain a magnet powder with low magnetic properties. In addition, it is a manufacturing method that is difficult to produce in an appropriate amount for mass production of anisotropic magnet powder having excellent magnetic properties.
[0003]
In contrast to such a manufacturing method, the present inventor has already developed a method for manufacturing anisotropic magnet powder that can provide very excellent magnetic properties. This manufacturing method is called a d-HDDR method in order to distinguish it from the HDDR method because the magnetic powder obtained has different characteristics and the process contents and the like are greatly different from those of the HDDR method. This d-HDDR method is provided with a plurality of steps with different temperatures and hydrogen pressures, and the reaction rate between the RFeB alloy and hydrogen is controlled gently, so that an anisotropic magnet powder excellent in magnetic properties can be obtained. It is a feature. Specifically, the RFeB alloy sufficiently absorbs hydrogen at room temperature, the high-temperature hydrogenation step that causes hydrogenation / disproportionation reaction under low hydrogen pressure, and the highest possible hydrogen pressure. It was supposed to be mainly composed of four processes, a first exhaust process for gradually dissociating hydrogen and a second exhaust process for removing hydrogen from the subsequent material. Details of each process are disclosed in the following Patent Documents 5 and 6, Non-Patent Document 1, and the like.
[0004]
[Patent Document 1]
US Pat. No. 4,851,058
[Patent Document 2]
US Pat. No. 5,411,608
[Patent Document 3]
JP-A-2-4901
[Patent Document 4]
JP 11-31610 A
[Patent Document 5]
Japanese Patent No. 3250551
[Patent Document 6]
JP 2002-93610 A
[Non-Patent Document 1]
Journal of the Japan Society of Applied Magnetics, 24 (2000), p. 407
DISCLOSURE OF THE INVENTION
[Problems to be solved by the invention]
[0005]
According to the d-HDDR method, an anisotropic magnet powder having excellent magnetic properties can be obtained, but higher magnetic properties are required for motor drive motor magnets and the like. Further, as the production amount increases, the amount of heat generated or the amount of heat absorbed during the reaction between the RFeB alloy and hydrogen increases, and the temperature of the processing atmosphere tends to change locally. For this reason, in the conventional manufacturing method, the temperature change cannot always be suppressed skillfully, and it is not easy to stably produce anisotropic magnetic powder having high magnetic properties.
[0006]
The present invention has been made in view of such circumstances. That is, it aims at providing the manufacturing method of the anisotropic magnet powder which has the magnetic property which was excellent so that it exceeded the past. Another object of the present invention is to provide a production method capable of stably producing the anisotropic magnet powder having high magnetic properties even during mass production.
[0007]
[Means for Solving the Problems]
The present inventor has intensively studied to solve this problem, repeated trial and error and repeated various systematic experiments. As a result, the process between the conventional high-temperature hydrogenation process and the controlled exhaust process was reviewed, and high-temperature hydrogenation was performed. After the treatment process, the structure stabilization process that increases at least one of the temperature and the hydrogen partial pressure is performed, and then the conventional controlled exhaust process is performed. I found out that I could obtain it. It was also confirmed that this was very suitable for mass production, and the present invention was completed.
[0008]
The method for producing anisotropic magnet powder of the present invention uses an RFeB-based alloy containing, as main components, a rare earth element containing yttrium (Y) (hereinafter referred to as “R”), boron (B), and iron (Fe). A predetermined first processing pressure (hereinafter referred to as “P1”) at a hydrogen partial pressure of 10 to 100 kPa and a predetermined first processing temperature (hereinafter referred to as “T1”) at a temperature of 953 to 1133K. A high-temperature hydrogenation step to maintain a processing atmosphere,
The RFeB alloy after the high-temperature hydrogenation step is subjected to a second treatment pressure (hereinafter referred to as “P2”) having a hydrogen partial pressure of 10 kPa or more. so At a second processing temperature (hereinafter referred to as “T2”) at a temperature of 1033 to 1213K. Yes, and Meet T2> T1 or P2> P1 You A tissue stabilization process that is maintained in a processing atmosphere;
The RFeB-based alloy after the structure stabilization step is subjected to a third treatment pressure (hereinafter referred to as “P3”) with a hydrogen partial pressure of 0.1 to 10 kPa. And P3 <P2 A controlled exhaust process of maintaining a processing atmosphere at a third processing temperature (hereinafter referred to as “T3”) in a temperature of 1033 to 1213K;
A forced exhaust process for removing residual hydrogen (H) from the RFeB-based alloy after the controlled exhaust process;
It is characterized by providing.
[0009]
The manufacturing method of the present invention is most different from the conventional d-HDDR method in that a structure stabilization process is newly established between both the high-temperature hydrogenation process and the controlled exhaust process. The structure stabilization process is characterized in that it is a process in which at least one of the treatment temperature and the hydrogen partial pressure is increased with respect to the high-temperature hydrotreatment process.
[0010]
In this way, after the high-temperature hydrogenation step, a structure stabilization step for increasing at least one of temperature and hydrogen partial pressure is performed, and further, a controlled exhaust step is performed to obtain a magnet powder with excellent magnetic properties that has never been obtained before. It was. Furthermore, according to this manufacturing method, it has been found that the anisotropic magnet powder having very high magnetic properties can be stably mass-produced.
[0011]
The reason why the production method of the present invention exhibits such excellent effects is not necessarily clear, but at present, it is considered as follows.
The conventional d-HDDR method basically includes the following four steps.
<1> In the low-temperature hydrogenation process, hydrogen pressure is applied in the temperature range below the hydrogenation / disproportionation reaction so that the hydrogenation / disproportionation reaction in the next process (high-temperature hydrogenation process) proceeds slowly. Dissolve hydrogen sufficiently.
<2> Thereafter, in the high-temperature hydrogenation step, the reaction is allowed to proceed while absorbing hydrogen under a predetermined pressure at a predetermined temperature in order to cause a hydrogenation / disproportionation reaction.
<3> Thereafter, in the controlled exhaust process, the reaction is allowed to proceed slowly by performing dehydrogenation under a relatively high predetermined pressure at the same temperature as the high-temperature hydrogenation process in order to cause a recombination reaction.
<4> Further, in the forced exhaust process, the dehydrogenation process is performed to remove residual hydrogen, and the process is completed. The three-phase decomposition proceeds as slowly as possible and recombines as slowly as possible.
[0012]
In order to develop a method for producing a magnetic powder having magnetic properties that are more excellent than ever, the present inventor has intensively studied the relationship between the above-mentioned various treatments and the structure, and reconsidered the conventional d-HDDR method.
[0013]
In the conventional high-temperature hydrogenation process, the hydrogenation / disproportionation reaction proceeds as slowly as possible. However, the hydrogenation / disproportionation reaction is not sufficiently completed, and a 2-14-1 phase (R2Fe14B phase) remains or a precipitate to be hydrocracked remains, It seemed that the magnetic characteristics that should have been originally exhibited were not sufficiently extracted. If the hydrogenation / disproportionation reaction is not completely completed, it is difficult to obtain uniform crystal grains after the recombination reaction. As a result, for example, the magnet powder becomes a mixed grain structure, and the iHc may be lowered, the squareness of the magnetic curve may be lowered, and (BH) max may be lowered.
[0014]
In general, the chemical reaction is faster at the beginning of the reaction, but gradually decreases. For this reason, it is said that the reaction is not completed unless it is kept for a long time. That is, the closer the reaction is to the end, the less likely it is to proceed. In order to slow down the reaction rate here, simply increasing the time of the high-temperature hydrogenation process and trying to complete the hydrogenation / disproportionation reaction. Since the time was too long, tissue deterioration (for example, coarsening of the tissue, etc.) occurred, and the magnetic properties were lowered.
[0015]
The present inventor has conceived the following in order to sufficiently complete the hydrogenation / disproportionation reaction without coarsening of the structure. That is, while the hydrogenation / disproportionation reaction proceeds as slowly as possible in the initial stage where the reaction rate is relatively fast, the reaction rate gradually decreases as it is, and a long time is required until the reaction is completed. Therefore, at the end of the reaction, it was considered effective to increase the reaction rate of the hydrogenation / disproportionation reaction and complete the reaction promptly.
[0016]
The hydrogenation / disproportionation reaction is a unique reaction controlled by both temperature and hydrogen partial pressure. The present inventor studied a means for speeding up the reaction by controlling the processing temperature and the hydrogen partial pressure by taking advantage of this feature. That is, if the treatment temperature was increased, the driving force of the hydrogenation / disproportionation reaction increased and the reaction was considered to be completed quickly. In addition, it was considered that even when the hydrogen partial pressure was increased, the reaction was completed quickly as in the case of increasing the treatment temperature.
[0017]
As described above, if at least the hydrogen pressure or the treatment temperature is increased at the end of the hydrogenation / disproportionation reaction, the hydrogenation / disproportionation reaction can be completed quickly.
[0018]
The present invention solves the above-mentioned problems by newly providing a structure stabilization process between the high-temperature hydrogenation process and the controlled exhaust process. For this reason, it has become possible to independently increase the processing temperature ranges of the conventional high-temperature hydrogenation process and the controlled exhaust process. For example, in the case of the conventional d-HDDR process, the process temperature range between the high-temperature hydrogenation process and the controlled exhaust process is as narrow as 1033 to 1133K. On the other hand, in the case of the present invention, the processing temperature range of the high-temperature hydrogenation process is 953 to 1133 K, the processing temperature range of the controlled exhaust process is 1033 to 1213 K, and the processing temperature range is expanded to about twice the conventional temperature range. I was able to.
[0019]
As a result, the amount of treatment increased, and it became possible to perform each process within an appropriate temperature range even with rapid heat generation in the high-temperature hydrogenation process or rapid heat absorption in the controlled exhaust process. Specifically, for example, by processing the high-temperature hydrogenation process at a lower temperature side within an appropriate temperature range and the control exhaust process at a higher temperature side within an appropriate temperature range, Each process can be processed within an appropriate temperature range. In addition, since the temperature processing range of each process can be expanded, the temperature management of each process becomes very easy.
[0020]
Thus, even when the throughput is increased, the high-temperature hydrogenation process proceeds in a temperature range suitable for hydrogenation / disproportionation reactions, and the controlled exhaust process is stable in a temperature range suitable for recombination reactions. As a result, an anisotropic magnet powder excellent in both Br and iHc and thus excellent in (BH) max and having high magnetic properties can be stably obtained even during mass production.
BEST MODE FOR CARRYING OUT THE INVENTION
[0021]
Embodiment
Hereinafter, the present invention will be specifically described with reference to embodiments.
(1) RFeB alloy
The RFeB alloy is mainly composed of a rare earth element (R) containing Y, B, and Fe. A typical RFeB alloy is an ingot having R2Fe14B as a main phase, or a coarse powder or a fine powder obtained by pulverizing the ingot.
[0022]
R is a rare earth element including Y, but R is not limited to one element, but may be a combination of a plurality of rare earth elements, or a part of the main element replaced with another element. .
[0023]
Such R consists of scandium (Sc), yttrium (Y), and a lanthanoid. However, as an element having excellent magnetic properties, R is Y, lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), gadolinium (Gd), terbium (Tb), dysprosium. It is preferable to comprise at least one of (Dy), holmium (Ho), erbium (Er), thulium (Tm) and lutetium (Lu). In particular, from the viewpoint of cost and magnetic properties, it is preferable that R is one or more of Pr, Nd, and Dy.
[0024]
The RFeB-based alloy preferably contains 11 to 16 at% R and 5.5 to 15 at% B when the main component is iron and the whole is 100 atomic% (at%). When R is less than 11 at%, the αFe phase is precipitated and the magnetic characteristics are deteriorated. When it exceeds 16 at%, the R 2 Fe 14 B phase is decreased and the magnetic characteristics are deteriorated. When B is less than 5.5 at%, soft magnetic R ₂ Fe ₁₇ This is because when the phase is precipitated and the magnetic properties are lowered and the content exceeds 15 at%, the R2Fe14B phase is reduced and the magnetic properties are lowered. In addition, when B is increased (10.8 at% or more), precipitation of α-Fe which is the primary crystal is suppressed, and precipitation of α-Fe which causes a decrease in magnetic properties is suppressed. It is possible to omit the homogenization heat treatment step that was considered indispensable for improvement. Thereby, further cost reduction of magnet powder etc. can be achieved.
[0025]
The RFeB-based alloy further preferably contains at least one of gallium (Ga) or niobium (Nb), and more preferably contains both. Ga is an element effective for improving the coercive force iHC of the anisotropic magnet powder. When the entire RFeB alloy is 100 at%, it is more preferable that Ga is contained in an amount of 0.01 to 2 at%, further 0.1 to 0.6 at%. If it is less than 0.01 at%, a sufficient effect cannot be obtained. If it exceeds 2 at%, iHc decreases conversely.
[0026]
Nb is an element effective for improving the residual magnetic flux density Br. When the entire RFeB alloy is 100 at%, it is more preferable that Nb is contained at 0.01 to 1 at%, further 0.1 to 0.4 at%. If it is less than 0.01 at%, sufficient effects cannot be obtained, and if it exceeds 1 at%, the hydrogenation / disproportionation reaction in the high-temperature hydrogenation process is slowed down. When Ga and Nb are added in combination, both iHc and anisotropic ratio of the anisotropic magnet powder can be improved, and the maximum energy product (BH) max can be increased.
[0027]
The RFeB alloy may contain Co. Co is an element that increases the Curie point of anisotropic magnet powder and is effective in improving heat resistance. When the entire RFeB alloy is 100 at%, it is more preferable that Co is contained in an amount of 0.1 to 20 at% or less and further 1 to 6 at%. If the amount is too small, there is no effect. However, since Co is expensive, an increase in the content is not preferable because the cost increases.
[0028]
In addition, the RFeB alloy may contain at least one of Ti, V, Zr, Ni, Cu, Al, Si, Cr, Mn, Zn, Mo, Hf, W, Ta, and Sn. These elements are effective in improving the coercive force and the squareness of the magnetization curve, and when the entire RFeB alloy is 100 at%, the total is preferably 3 at% or less. If the amount is too small, there is no effect, but if the amount is too large, a precipitated phase or the like appears to cause a decrease in coercivity.
[0029]
Further, it is preferable that the RFeB alloy contains 0.001 to 1.0 at% La apart from R. Thereby, an aged deterioration of anisotropic magnet powder and a hard magnet (for example, bond magnet) consisting thereof can be controlled. This is because La is an element having the highest oxidation potential among rare earth elements (RE). For this reason, La acts as a so-called oxygen getter, La is selectively (preferentially) oxidized over R (Nd, Dy, etc.), and as a result, oxidation of magnet powder and hard magnets containing La is performed. It is suppressed. Although use of Dy, Tb, Nd, Pr, etc. can be considered in place of La, La is more preferable from the viewpoint of the oxidation suppression effect and cost. When La is contained for such an intention, R in the RFeB alloy is a rare earth element other than La.
[0030]
The effect of improving the corrosion resistance by La is obtained from a trace amount in which La exceeds the level of inevitable impurities. When the inevitable impurity level amount of La is less than 0.001 at%, the lower limit of the La amount may be 0.001 at%, further 0.01 at%, 0.05 at%, or 0.1 at%. On the other hand, if La exceeds 1.0 at%, iHc is lowered, which is not preferable. Therefore, the La amount is more preferably 0.01 to 0.7 at%. Needless to say, the RFeB alloy contains inevitable impurities, and its composition is balanced with Fe.
[0031]
For the RFeB alloy, for example, an ingot melted and cast by various melting methods (high frequency melting method, arc melting method, etc.) or a raw material manufactured by a strip cast method can be used. Further, it is preferable that the RFeB-based alloy is a powder obtained by pulverizing an ingot, a strip, or the like because the d-HDDR treatment proceeds uniformly. For this pulverization, general hydrogen pulverization or mechanical pulverization can be used.
[0032]
(2) d-HDDR processing
In the production method of the present invention, four processes, ie, a high-temperature hydrogenation process, a structure stabilization process, a controlled exhaust process, and a forced exhaust process, are essential processes. However, these steps do not need to be performed continuously. Furthermore, it is preferable to provide a low-temperature hydrogenation process before the high-temperature hydrogenation process and a cooling process after the controlled exhaust process in consideration of mass productivity. From the viewpoint of expanding the use of hard magnets by improving the magnetic properties of anisotropic magnet powder and improving the heat resistance, corrosion resistance, etc. when the anisotropic magnet powder is made into a hard magnet (bonded magnet, etc.) It is preferable to perform a diffusion heat treatment step or the like. Hereinafter, each of these steps will be described.
[0033]
<1> Low temperature hydrogenation process
The low-temperature hydrogenation step is a step of holding the RFeB-based alloy in a hydrogen atmosphere having a temperature of 873 K or less, more preferably 723 K or less, before the high-temperature hydrogenation step. This process allows the RFeB alloy to sufficiently store hydrogen in a low temperature range where hydrogenation and disproportionation reactions do not occur, and facilitates the speed control of the hydrogenation and disproportionation reactions in the high temperature hydrogenation process. can do. However, since the hydrogen occlusion in the RFeB alloy can be combined with a high-temperature hydrogenation process in the case of a small amount of processing, this process is not an essential process in the production method of the present invention. Of course, it is needless to say that this step is preferably provided in view of processing a large amount of RFeB-based alloy and stably mass-producing anisotropic magnet powder having high magnetic properties.
[0034]
Since this step is performed in a temperature range where hydrogenation / disproportionation reaction does not occur, it is considered that the following reaction mainly occurs.
[Chemical 1]

That is, hydrogen only penetrates between the lattices or the grain boundaries of the RFeB-based alloy, and basically no phase transformation occurs in this step.
[0035]
Although it depends on the composition of the raw material alloy, hydrogenation / disproportionation reactions usually start at 873 to 1033K. If the temperature in this step is set to exceed 873K, partial structural transformation occurs. The tissue becomes uneven. This is not preferable because it causes the magnetic properties of the anisotropic magnet powder to be significantly reduced. Therefore, this step is preferably performed at a temperature of 873 K or lower, more preferably 723 K or lower, and more specifically in a temperature range of about room temperature to 573 K. The hydrogen pressure (partial pressure) during the low-temperature hydrogenation step is not particularly limited, but is preferably 30 to 100 kPa, for example. By setting the hydrogen pressure to 30 kPa or more, the time required to store hydrogen in the RFeB-based alloy can be shortened, and by setting the pressure within 100 kPa, hydrogen storage can be performed economically. Note that the treatment atmosphere may be configured not only with hydrogen gas but also with, for example, a mixed gas of hydrogen gas and inert gas. What is important is the hydrogen partial pressure, which is the same in the following steps.
[0036]
<2> High-temperature hydrogenation process
The high-temperature hydrogenation step is a step of maintaining the RFeB-based alloy in a processing atmosphere having a hydrogen component force of 10 to 100 kPa and a temperature of 953 to 1133K and a first processing temperature (T1). In this process, the structure of the RFeB alloy that occludes hydrogen is decomposed into three phases by this process (Fe phase, RH). ₂ Phase, Fe ₂ B phase). At this time, it is considered that the following hydrogenation / disproportionation reaction mainly occurs.
[Chemical 2]

That is, first, the RFeB-based alloy that occludes hydrogen is a hydride of Fe and R (RH). ₂ ) To form a lamellar lamellar structure. This Fe is considered to be in a state where B is dissolved in supersaturation. And, the lamellar structure has strain introduced only in one direction, and in the form along this strain, B, which was supersaturated in Fe, is tetragonal Fe. ₂ It is considered that B precipitates in one direction.
[0037]
Here, when the reaction rate is high, a lamellar structure in which strain is oriented in one direction is not formed, and Fe that precipitates out. ₂ The direction of B is also random. That is, the anisotropic rate decreases and Br also decreases. Therefore, in order to obtain anisotropic magnetic powder having high magnetic properties, it is preferable to proceed the reaction as slowly as possible. In order to perform this reaction rate gently, the upper limit of the hydrogen partial pressure is suppressed to 100 kPa in this step. However, if the hydrogen partial pressure is too small, it is not preferable because no reaction takes place or a large amount of untransformed tissue remains, leading to a decrease in coercive force, so the lower limit was set to 10 kPa.
[0038]
Further, when the treatment temperature in this step is less than 953K, the above reaction does not proceed, and when it exceeds 1133K, the supersaturated Fe is transformed into Fe. ₂ It becomes difficult for B to precipitate in one direction or the reaction rate is high, so that the lamellar structure is hardly formed, and eventually, Br of the magnetic powder is lowered. Therefore, this step is performed at the first set temperature (T1) in 953-1133K where the above reaction proceeds slowly. Details of preferable reaction rates and the like are described in Patent Document 5 and Non-Patent Document 1 described above.
[0039]
<3> Organization stabilization process
In the tissue stabilization process, the reaction rate at the end of the high-temperature hydrogenation process is increased to sufficiently complete the reaction, and the three-phase decomposition is reliably performed. For this reason, in the structure stabilization process, it is only necessary to appropriately select the processing temperature (T2) or the hydrogen partial pressure (P2) to form a processing atmosphere that increases the reaction rate at the end of the high-temperature hydrogenation process. Specifically, it is sufficient that at least T2> T1 or P2> P1 as compared with the treatment temperature (T1) and the hydrogen partial pressure (P1) during the high-temperature hydrogenation step. However, the purpose is not to make P2 and T2 in the structure stabilization process higher than P1 and T1 in the high-temperature hydrogenation process, but to improve the reaction rate at the end of the high-temperature hydrogenation process. Therefore, as long as the reaction rate increases, T2> T1 and P2 <P1 may be satisfied, or T2 <T1 and P2> P1 may be satisfied. For example, when P1 is 30 kPa, even if P2 is set to 20 kPa, the purpose of the tissue stabilization process can be sufficiently achieved if T2 is sufficiently higher than T1 more than canceling the effect of P2 <P1. Is done. Conversely, for example, when T1 is 1073K, even if T2 is set to 1048K, if P2 is sufficiently higher than P1 more than canceling the influence of T2 <T1, the purpose of the tissue stabilization process is Fully achieved.
[0040]
Of course, in order to make a smooth transition from the high-temperature hydrogenation step to the tissue stabilization step and stably obtain a magnet powder having high magnetic properties, the treatment atmosphere of the tissue stabilization step is T2> T1 and P2 ≧ P1 or P2>. It is better to satisfy the condition of P1 and T2 ≧ T1. That is, when the high temperature hydrogenation process is used as a reference, it means that at least one of the treatment temperature and the hydrogen partial pressure in the structure stabilization process is higher than those in the high temperature hydrogenation process. Under these conditions, the hydrogenation / disproportionation reaction in which the reaction progresses and the reaction rate decreases can be further promoted. Then, the hydrocracking of the remaining 2-14-1 phase after the high-temperature hydrogenation step and the precipitate to be hydrocracked proceed quickly.
[0041]
Here, the hydrocracking may be completed during the temperature raising process or the pressurizing process, but in any case, it is preferable to hold the hydrocracking until the hydrocracking is almost completely completed under the structure stabilization process.
[0042]
The structure stabilization process is performed in order to hydrocrack the 2-14-1 phase remaining in the high-temperature hydrogenation process as a pretreatment and the precipitate to be hydrocracked. Considering this point, the range of the hydrogen partial pressure P2 is set to 10 kPa or more, and the range of the processing temperature T2 is set to 1033 to 1213K.
[0043]
When the hydrogen partial pressure is less than 10 kPa, recombination is started, and as a result, the magnetic properties are deteriorated. On the other hand, the upper limit is not particularly limited. Rather, the higher the P2, the higher the effect of the tissue stabilization process. However, the upper limit of P2 is preferably 200 kPa in consideration of production convenience such as the cost and durability of the processing furnace.
[0044]
The reason why the treatment temperature is set to 1033 to 1213K is that when it is 1033K or less, the hydrocracking of the remaining 2-14-1 phase or the precipitate to be hydrocracked does not proceed, and the magnetic characteristics are deteriorated. On the other hand, the reason why the upper limit is set to 1213K is that the tissue deteriorates and the magnetic characteristics are lowered.
[0045]
<4> Control exhaust process
In the controlled exhaust process, the RFeB alloy after the structure stabilization process is a third process pressure (T3) at a third process pressure (P3) with a hydrogen partial pressure of 0.1 to 10 kPa and a temperature of 1033 to 1213K. This is a step of maintaining the processing atmosphere.
[0046]
In this process, the RH during the three-phase decomposition produced in the high-temperature hydrogenation process that is the previous process ₂ Hydrogen is removed from the phase and Fe ₂ R with uniform crystal orientation centered on B ₂ Fe ₁₄ B ₁ The phases are recombined. At this time, it is considered that the following recombination reaction mainly occurs.
[Chemical 3]

This recombination reaction also preferably proceeds as slowly as possible. When the reaction rate is fast, Fe ₂ The crystal orientation centered on B is distorted and recombined R ₂ Fe ₁₄ B ₁ This is because the phase anisotropy is also lowered and the magnetic properties are lowered.
[0047]
Therefore, in this step, the third processing pressure (P3) is set to 0.1 to 10 kPa. When rapid exhaust is performed so that the hydrogen partial pressure is less than 0.1 kPa, the exhaust rate changes between the alloy material near the exhaust port and the alloy material far from the exhaust port, and the recombination reaction rate tends to be uneven. . Moreover, since this recombination reaction is an endothermic reaction, it will also cause the temperature nonuniformity by a place, and synergistically leads to the magnetic characteristic fall of the whole anisotropic magnet powder. On the other hand, when the hydrogen partial pressure exceeds 10 kPa, the recombination reaction does not proceed, the reverse structure transformation becomes insufficient, and an anisotropic magnet powder with high iHc cannot be obtained.
[0048]
In addition, when the processing temperature in this step is less than 1033K, the above reaction does not proceed. On the other hand, when it exceeds 1213K, the recombination reaction does not proceed properly. Cannot be obtained. Therefore, this step is performed at the third treatment temperature (T3) in 1033 to 1213K where the above reaction proceeds slowly. Details such as a preferable reaction rate in this case are also described in Patent Document 5 and Non-Patent Document 1 described above.
[0049]
<5> Forced exhaust process
The forced exhaust process is a process of removing residual hydrogen (residual hydrogen) from the RFeB alloy (RFeBHx) after the controlled exhaust process. At this time, it is considered that the following reaction mainly occurs.
[Formula 4]

The processing temperature, the degree of vacuum, etc. in this step are not particularly limited, but it is preferable to evacuate to 1 Pa or less at a temperature similar to or lower than T3. This is because if the degree of vacuum is weak, hydrogen may remain, leading to deterioration of magnetic properties. Further, if the treatment temperature is too low, it takes a long time for exhaust, and if it is too high, the crystal grains become coarse, which is not preferable.
[0050]
By the way, the forced exhaust process need not be performed continuously with the controlled exhaust process. A cooling step for cooling the alloy material may be inserted after the controlled exhaust step and before this step. Providing the cooling process is effective, for example, when the RFeB alloy obtained after the controlled exhaust process is transferred to another processing furnace or the like and the forced exhaust process or the like is batch-processed during mass production. It is convenient to provide a cooling step when the RFeB alloy is pulverized to a predetermined particle size. In addition, when performing a diffusion heat treatment described later, mixing of the RFeB alloy (R2Fe14B1Hx) and the diffusion material is facilitated by including this cooling step. Note that the diffusion heat treatment step in this case may be considered to also serve as the forced exhaust step in the present invention. That is, it may be considered that one form of the forced exhaust process is a diffusion heat treatment process.
[0051]
The cooling step does not matter the cooling state of the RFeB-based alloy, but is for easy handling, so the cooling temperature, the cooling method, the cooling atmosphere, etc. are not limited. Further, since the hydride has oxidation resistance, the RFeB-based alloy can be taken out into the atmosphere at room temperature. Naturally, after the cooling process, it is preferable to perform a forced exhaust process such as raising the temperature of the RFeB alloy (R2Fe14B1Hx) again and evacuating it.
[0052]
In addition, when a diffusion material is mixed with the RFeB alloy (R2Fe14B1Hx) after the controlled exhaust process and then the diffusion heat treatment process is performed, it is efficient to perform the forced exhaust process collectively after that process.
[0053]
(3) Diffusion heat treatment
Even with the d-HDDR treatment alone, an anisotropic magnet powder with sufficiently high magnetic properties can be obtained. However, an anisotropic magnet powder with improved coercive force and further corrosion resistance can be obtained by performing the diffusion heat treatment described below.
[0054]
This diffusion heat treatment is basically performed by mixing a diffusion material made of Dy or the like into an RFeB alloy (R2Fe14B1Hx) after the controlled exhaust process or an RFeB alloy (anisotropic magnet powder) after the forced exhaust process. And a diffusion heat treatment step in which the mixed powder is heated to diffuse Dy or the like on the surface and inside of the RFeB alloy.
[0055]
<1> Diffusion material
As long as the diffusion material contains at least one element composed of dysprosium (Dy), terbium (Tb), neodymium (Nd), praseodymium (Pr), or lanthanum (La) (hereinafter referred to as “R1”). good. For example, it contains at least one element, alloy, compound or hydride (R1 material) of the element (R1) composed of Dy, Tb, Nd, Pr and La. The hydride includes a hydride of a simple substance, an alloy or a compound of R1. Furthermore, a mixture thereof may be used. The form of the diffusing material before the mixing step is not limited, but a material that easily becomes a mixed powder by the mixing step is preferable. Therefore, a powdery diffusion material (diffusion powder) is preferably used as necessary, and uniform diffusion of R1 into the RFeB alloy is easy.
[0056]
The R1 material includes one or more transition elements (hereinafter referred to as “TM”) of a 3d transition element and a 4d transition element, and when TM diffuses uniformly along the surface and inside of the RFeB-based alloy together with R1 in the diffusion heat treatment step. More preferred. Thereby, it is possible to further improve the coercive force and lower the permanent demagnetization factor. The 3d transition element is atomic number 21 (Sc) to atomic number 29 (Cu), and the 4d transition element is atomic number 39 (Y) to atomic number 47 (Ag). In particular, Group 8 Fe, Co, and Ni are effective in improving magnetic properties. Further, the diffusion material may be prepared by separately preparing powder of R1 material and powder of TM alone, alloy, compound or hydride (TM material) and mixing them. In addition, the compound as used in this specification includes an intermetallic compound. The hydride includes one containing hydrogen in a solid solution state.
[0057]
Such diffusion materials are, for example, dysprosium powder, dysprosium cobalt powder, dysprosium iron powder, dysprosium hydride powder or dysprosium cobalt hydride powder, dysprosium iron hydride powder. In particular, when R1 is Dy, the coercive force of the anisotropic magnet powder is improved, and when TM is Co, the Curie point of the anisotropic magnet powder is improved. Furthermore, when Fe is contained in TM, cost reduction can be achieved.
[0058]
In particular, the diffusing material is preferably a diffusing powder having an average particle size of 0.1 to 500 μm, which facilitates diffusion of R1. Diffusing powder having an average particle size of less than 0.1 μm is difficult to produce, and when the average particle size exceeds 500 μm, uniform mixing with the RFeB alloy becomes difficult. And the average particle diameter is more preferable in it being 1-50 micrometers.
[0059]
Such a diffusion powder can be obtained by subjecting the R1 material to general hydrogen pulverization, dry or wet mechanical pulverization (jaw crusher, disk mill, ball mill, vibration mill, jet mill, etc.) and the like. However, hydrogen pulverization of the R1 material is efficient, and hydride powder is preferably used as the diffusion powder from this viewpoint. Furthermore, it is more preferable to perform dry or wet mechanical pulverization after hydrogen pulverization.
[0060]
<2> RFeB alloy before diffusion heat treatment
It is efficient to use the RFeB alloy mixed with the diffusing material obtained after the controlled exhaust process or after the forced exhaust process, which is also preferable from the viewpoint of achieving magnetic properties of the anisotropic magnet powder. When the RFeB-based alloy (R2Fe14B1Hx) after the controlled exhaust process is used, it is preferable to perform a dehydrogenation process before the diffusion heat treatment process or perform a diffusion heat treatment process also as a forced exhaust process. That is, the mixing step is a step of mixing the RFeB-based alloy hydride powder obtained after the controlled exhaust step and a diffusion powder made of a hydride powder containing R1 into a mixed powder, and the diffusion heat treatment step May be a process that also serves as the forced exhaust process for removing residual hydrogen from the mixed powder.
[0061]
The form of the RFeB-based alloy is not limited, but the average particle size is preferably 200 μm or less in consideration of the mixing property with the diffusing material, diffusibility, and the like.
[0062]
<3> Mixing process
The mixing step is a step of mixing the RFeB alloy and the diffusion material into a mixed powder. For the mixing step, a Henschel mixer, a rocking mixer, a ball mill, or the like can be used. Further, it is particularly preferable to use a rotary kiln furnace or a rotary retort furnace provided with a mixing function in the furnace of the diffusion heat treatment step. In order to uniformly mix the RFeB alloy and the diffusing material, it is preferable to appropriately grind and classify each raw material. By performing classification, it becomes easy to form a bonded magnet or the like. In addition, the mixing step is preferably performed in an antioxidant atmosphere (for example, an inert gas atmosphere or a vacuum atmosphere) in order to suppress oxidation of the anisotropic magnet powder.
[0063]
By the way, the mixing of the diffusing material is preferably performed at a ratio of 0.1 to 3.0% by mass when the entire mixed powder is 100% by mass. By appropriately adjusting the mixing ratio of the diffusing material, an anisotropic magnet powder that exhibits high magnetic properties excellent in all of coercive force, residual magnetic flux density and squareness and excellent in permanent demagnetization rate can be obtained. .
[0064]
<4> Dehydrogenation process
The dehydrogenation step is a step of removing residual hydrogen in the mixed powder. Here, when at least one of the RFeB alloy and the diffusion material is a hydride, in order to contain the hydrogen, a dehydrogenation step before the diffusion heat treatment step or a diffusion heat treatment step is necessary.
[0065]
When a diffusion material is mixed with the RFeB-based alloy before the forced exhaust process and a diffusion heat treatment is performed, this process also serves as the forced exhaust process of the d-HDDR process. When diffusion heat treatment is performed by mixing a diffusion material made of hydride into the RFeB alloy after the forced exhaust process, it is necessary to separately perform a dehydrogenation process before the diffusion heat treatment process. The dehydrogenation step in this case may be performed in a vacuum atmosphere of 1 Pa or less and 1023 to 1123K, for example. The reason why the pressure is set to 1 Pa or less is that when 1 Pa is exceeded, hydrogen remains, and the coercive force of the anisotropic magnet powder is reduced. The reason why it is set to 1023 to 1123K is that if it is less than 1023K, the removal rate of residual hydrogen is low, and if it exceeds 1123K, the crystal grains become coarse.
[0066]
<5> Diffusion heat treatment process
The diffusion heat treatment step is a step in which the mixed powder obtained after the mixing step is heated to diffuse R1 of the diffusion material on the surface and inside of the RFeB alloy.
[0067]
R1 also functions as an oxygen getter and suppresses oxidation of anisotropic magnet powder and a hard magnet using the same. Therefore, even when the magnet is used in a high temperature environment, performance deterioration due to oxidation is effectively suppressed and prevented. And since the heat resistance of magnet powder improves, the use is expanded.
[0068]
The diffusion heat treatment step is preferably performed in an oxidation-preventing atmosphere (for example, in a vacuum atmosphere), and the treatment temperature is preferably 673 to 1173 K, and particularly preferably the temperature T3 or less in the controlled exhaust step. If it is less than 673K, the diffusion rate of R1 or TM is slow and not efficient, and if it exceeds 1173K or T3, the crystal grains become coarse, which is not preferable. Further, rapid cooling is preferable for preventing crystal grain coarsening.
[0069]
(4) Other
The anisotropic magnet powder obtained by the production method of the present invention is formed into a sintered magnet or bonded magnet having a desired shape. In particular, the anisotropic magnet powder is effective for bonded magnets that have a high degree of freedom in shape and do not require high-temperature heating. This bonded magnet is obtained by adding and kneading a thermosetting resin, thermoplastic resin, coupling agent or lubricant to the obtained anisotropic magnet powder, and then compression molding, extrusion molding, injection molding, etc. in a magnetic field. Manufactured.
【Example】
[0070]
Hereinafter, an example is given and the present invention is explained in detail.
(Manufacture of test materials)
(1) First embodiment
In order to confirm the effect of the d-HDDR treatment according to the present invention, the sample Nos. Shown in Table 1 and Table 2, respectively. 1-26 and Sample No. C1-C24 specimens were produced. As raw materials used at this time, RFeB alloys having four different compositions were prepared. Each of these compositions is shown in Table 3. The unit of Table 3 is at%, and the whole alloy is shown as 100 at%. Hereinafter, each RFeB-based alloy is referred to as an alloy A, an alloy B, or the like by using symbols A to D shown in Table 3.
[0071]
These alloys A to D were produced as follows. In each alloy, commercially available raw materials were weighed so as to have a desired composition, melted using a high-frequency melting furnace, and cast to produce a 100 kg ingot. The alloy ingot was heated in an Ar gas atmosphere for 1413 K × 40 hours to homogenize the structure (homogenized heat treatment). The alloy ingot was further coarsely pulverized to a mean particle size of 10 mm or less using a jaw crusher to obtain alloys AD having different compositions. Alloy D was coarsely pulverized without being subjected to homogenization heat treatment after melting and casting.
[0072]
Next, as shown in Tables 1 and 2, a large number of specimens were manufactured for each specimen by changing the type of alloy used and the content of the process. The processing amount of each specimen was 12.5 g. The alloy used for each test material was put in a processing furnace, and a common low-temperature hydrogenation step of room temperature x 100 kPa x 1 hour was performed. Subsequently, a high temperature hydrogenation step for 180 minutes was performed. The temperature (T1) and hydrogen partial pressure (P1) of this high-temperature hydrogenation process are shown in Tables 1 and 2 for each specimen.
[0073]
In addition, sample No. in Table 1 Only 26, without performing the said low temperature hydrogenation process, it heated up from room temperature to the predetermined temperature in predetermined hydrogen pressure, and performed the high temperature hydrogenation process directly. Sample No. In the case of 26, the alloy ingot used a block of about 5 to 10 mm.
[0074]
Further, a controlled exhaust process with a hydrogen partial pressure of 1 kPa was performed for 90 minutes. The temperature (T3) of this controlled exhaust process is shown in Tables 1 and 2 for each specimen. However, sample no. In the case of C1 to C16, T3 = T1 because the high-temperature hydrogenation process and the controlled exhaust process were performed at the same temperature. Finally, a forced evacuation step was performed for 30 minutes at the same temperature as the controlled evacuation step and a hydrogen partial pressure in the processing furnace of 1 Pa or less.
[0075]
By the way, sample no. In the case of 1-26, the structure stabilization process was provided between said high temperature hydrogenation process and control exhaust process. In the tissue stabilization process, at least one of the treatment temperature and the hydrogen partial pressure was increased. These process patterns are shown in FIGS. In addition, although temperature rising (T1-> T2) in a structure | tissue stabilization process was all performed in 5 minutes, the holding time after that was changed for every test material. The details are shown in Table 1.
[0076]
Furthermore, sample no. 1 to 26, sample No. In Nos. 19 to 23, after the controlled exhaust process, an RFeB alloy hydride was transferred to a cooling furnace and cooled to room temperature. And after this cooling process, the said forced exhaust process which heats again and evacuates was performed. The process pattern at this time is shown in FIG.
[0077]
Sample No. In C1 to C16, the structure stabilization process was not performed, and the high temperature hydrogenation process was directly transferred to the controlled exhaust process. The process pattern at this time is shown in FIG.
[0078]
Sample No. In C17 to C22, the above-described tissue stabilization step was provided, but T1 during the high-temperature hydrogenation step, T2, P2 during the tissue stabilization step, and T3 during the controlled exhaust step were out of the preferred range referred to in the present invention. .
[0079]
Sample No. C23 is obtained by raising the temperature in the processing furnace from T1 to T3 over 5 minutes after the lapse of 5 minutes from the start of the controlled exhaust process without providing the above-described structure stabilization process. Sample No. C24 is obtained by increasing the temperature in the processing furnace from T1 to T3 over 5 minutes after the lapse of 15 minutes from the start of the controlled exhaust process without providing the structure stabilization process. These process patterns are shown in FIG.
[0080]
(2) Second embodiment
In order to confirm the effect when the diffusion heat treatment was performed in addition to the d-HDDR treatment, the sample Nos. Shown in Table 4 were used. Sample materials 27 to 47 were produced. Six kinds of rare earth alloys having different compositions were prepared as raw materials for the diffusion material used at this time. Their respective compositions are shown in Table 5. The unit of Table 5 is at%, and the whole alloy is shown as 100 at%. In the following, each rare earth alloy is distinguished using symbols a to f shown in Table 5.
[0081]
Sample No. In the production of 27 to 47, first, any of the alloys B to D shown in Table 3 is subjected to the low temperature hydrogenation step, the high temperature hydrogenation step, the structure stabilization step, and the controlled exhaust step, and the cooling step is performed to room temperature. An RFeB alloy hydride powder (average particle size: 100 μm) obtained by cooling was prepared.
[0082]
Next, a hydride powder of any of the rare earth alloys a to f was prepared as a diffusion material. The average particle diameters of the hydride powders of the rare earth alloys a to f were different, but all were within 5 to 30 μm.
[0083]
The mixed powder obtained by mixing both the above powders (mixing step) was subjected to a diffusion heat treatment step, and sample No. 27-47 anisotropic magnet powder was obtained. The process pattern at this time is shown in FIG.
[0084]
Sample No. No. 44 uses a rare earth alloy b powder (average particle size: 5 μm) as a diffusion material instead of the hydride.
[0085]
Sample No. No. 40 used anisotropic magnet powder after the forced exhaust process instead of the hydride powder of the RFeB alloy in the controlled exhaust process. That is, the anisotropic magnet powder which did not perform the cooling process after the controlled exhaust process but performed the forced exhaust process subsequently was used. The process pattern at this time is shown in FIG.
[0086]
Sample No. No. 47 used anisotropic magnet powder that had been subjected to a forced evacuation process by cooling once after the controlled evacuation process and further heating in vacuum. The process pattern at this time is shown in FIG.
[0087]
These sample Nos. The conditions of the d-HDDR treatment and diffusion heat treatment performed in the production of Nos. 27 to 47 are as follows, and the conditions that differ for each test material are shown individually in Table 4. That is, RFeB-based alloy throughput: 12.5 g, low-temperature hydrogenation step: room temperature x 100 kPax for 1 hour, high-temperature hydrogenation step: 1053 Kx for 180 minutes, structure stabilization step: temperature rise for 5 minutes → hold for 10 minutes, controlled exhaust step: 1113 Kx1 kPax for 90 minutes Forced exhaustion process: 1113 K × 10 Pa or less × 30 minutes, dehydrogenation / diffusion heat treatment process: 1073 K × 1 Pa or less × 1 hour.
[0088]
(3) Third embodiment
In order to confirm the effect of mass production of the d-HDDR treatment and the diffusion heat treatment, the sample Nos. Shown in Table 6 and Table 7 were further used. 48-54 and sample no. C25 and C26 specimens were produced. Sample No. 48-51 and sample no. C25 is only d-HDDR treatment, and sample No. 52-54 and sample no. C26 is further subjected to diffusion heat treatment. All of the RFeB-based alloys used are alloy B, and the treatment amount is 10 kg. Further, as the diffusion material, hydride powder of rare earth alloy b was used. This diffusion material was mixed with the hydride of the RFeB alloy after the controlled exhaust process at a ratio of 1 to 3% by mass with respect to the entire mixed powder. Details of the other steps are shown in Tables 6 and 7.
[0089]
(Measurement of test materials)
The magnetic properties ((BH) max, iHc and Br) at room temperature of each obtained magnet powder were measured. The measurement used VSM. As a measurement sample, first, magnet powder was classified to a particle diameter of 75 to 106 μm, and the classified magnet powder was solidified and molded with paraffin so that the demagnetizing factor was 0.2. After orientation in a magnetic field of 1.5T, it was magnetized at 4.5T, and its (BH) max, iHc and Br were measured by VSM.
[0090]
(Evaluation)
(1) About d-HDDR processing
Sample No. 1-26 and sample no. As is clear when C1 to C24 are compared, Sample No. In the case of 1 to 26, the magnetic properties are improved as a whole by applying a structure stabilization process between the high-temperature hydrogenation process and the controlled exhaust process. For example, among the anisotropic magnet powders made of the alloy B having the same composition, when the one having the maximum maximum energy product ((BH) max) is observed, the conventional sample No. C7 is 360 (kJ / m ^Three ), While sample no. 4 is 372 (kJ / m ^Three ) Has improved. Furthermore, among the anisotropic magnet powders made of the alloy C, when the one with the maximum maximum energy product ((BH) max) is observed, the conventional sample no. C12 is 360 (kJ / m ^Three ), While sample no. 19 is 382 (kJ / m ^Three ) Has improved. From the above, the anisotropic magnet powder produced by the production method of the present invention is superior to the conventional production method.
[0091]
Although the case of the alloy B has been described, anisotropic magnet powders made of other alloys have the same tendency when compared with those of the same composition. Sample No. Regarding 19-23, the cooling process was provided between the control exhaust process and the forced exhaust process. Even in this process order, excellent magnetic properties were obtained, and it was confirmed that mass production was easy.
[0092]
Next, sample No. Even if a structure stabilization process is provided between the high-temperature hydrogenation process and the controlled exhaust process from C17 to C22, preferable magnetic characteristics cannot be obtained as long as they are out of a suitable temperature range and a suitable hydrogen partial pressure range. .
[0093]
Regarding the temperature, sample no. C23 and C24 were sample No. As can be seen from a comparison with 4 etc., when the temperature was raised inappropriately in the controlled exhaust process, improvement in magnetic properties could not be expected.
[0094]
Sample No. 11-15 or sample no. As can be seen from 19 to 22, the coercive force (iHc) could be improved by increasing the retention time during the tissue stabilization process. Therefore, the heat resistance of the anisotropic magnet powder can be increased by increasing the holding time. This tendency is shown in Sample No. 11-15 and sample no. From comparison with 19-22, it was observed irrespective of the presence or absence of the cooling process provided between the controlled exhaust process and the forced exhaust process.
[0095]
Sample No. From 17 to 18, it was found that when the hydrogen partial pressure (P2) during the structure stabilization process was increased, the magnetic properties were improved as compared with C5 of the conventional d-HDDR process. However, according to the inventor's research, it has been found that even if P2 is increased beyond a certain level, the effect of improving the magnetic characteristics tends to be saturated. Considering the cost and durability of the processing furnace at the time of mass production, the upper limit of P2 in the structure stabilization process is preferably 200 kPa.
[0096]
Sample No. 24 is an example showing that T2> T1 and P2 <P1 may be satisfied. When P1 is 30 kPa as in this example, even if P2 is 20 kPa, if T2 is sufficiently increased from 1053K to 1133K of T1 more than canceling the effect of P2 <P1, the tissue is stabilized. The purpose of the process is fully achieved. Sample No. 25 is an example showing that T2 <T1 and P2> P1 may be satisfied. When T1 is 1113K as in this embodiment, even if T2 is set to 1103K, if P2 is sufficiently increased from 30 kPa of P1 to 200 kPa more than canceling the influence of T2 <T1, the structure is stabilized. The purpose of the process is fully achieved. As a result, sample no. Both 24 and 25 have good magnetic properties.
[0097]
Sample No. 26 and Sample No. Comparing C5, both have the same alloy composition and high-temperature hydrogenation process conditions, but differ depending on the presence or absence of the low-temperature hydrogenation process and the structure stabilization process. From the comparison between the two, it was found that the magnetic properties of (BH) max and iHc can be enhanced by performing the structure stabilization step without performing the low-temperature hydrogenation step.
[0098]
(2) Diffusion heat treatment
Sample No. 27-47 and sample no. Compared with 1 to 26, iHc is generally increased by diffusion heat treatment. This is important in terms of imparting heat resistance to the magnet. Sample No. 33 etc. and sample no. When compared with 41 to 43, the diffusion material is preferably about 0.5 to 1% by mass. Sample No. 33 and Sample No. Comparing with 44, it was also found that the diffusion material is sufficiently effective even if it is not a hydride.
[0099]
Sample No. From 27 to 29, even when diffusion heat treatment was performed, it was found that iHc can be increased by increasing the retention time during the tissue stabilization process. Therefore, also in this case, the heat resistance of the anisotropic magnet powder can be increased by lengthening the holding time of the structure stabilization step. Of course, sample no. As can be seen from 29 to 32, iHc can be improved by increasing the diffusion material, and the heat resistance of the anisotropic magnet powder can be increased.
[0100]
(3) Mass production
Sample No. 48 to 51 are sample Nos. No. 4 was used as a base for mass production. C25 is Sample No. It is intended for mass production based on C7. In either case, the magnetic properties tend to be somewhat deteriorated as the processing amount increases. 46-49 are sample Nos. The tendency was smaller than C25. Specifically, Sample No. C25 is Sample No. For C7, (BH) max is 42 (kJ / m ^Three For example, sample no. 48 is a sample No. 48. 4 to (BH) max is 20 (kJ / m ^Three Only). As described above, the manufacturing method of the present invention has a decrease in magnetic properties of 1/2 or less in the mass production stage as compared with the conventional manufacturing method. Therefore, the production method of the present invention is an industrially very effective production method, and an anisotropic magnet powder having high magnetic properties can be obtained not only at the laboratory level but also in mass production.
[0101]
Sample No. As can be seen from 48 to 51, even if the treatment amount is increased, iHc is improved by increasing the retention time during the tissue stabilization step, and the heat resistance of the anisotropic magnet powder can be enhanced.
[0102]
Specimen No. subjected to diffusion heat treatment 52-54 and sample no. Similarly, for C26, an anisotropic magnet powder with high magnetic properties can be obtained even during mass production by applying a tissue stabilization step, and by increasing the diffusion material, iHc is improved and the anisotropic magnet powder It was also found that heat resistance can be improved.
[0103]
[Table 1]

[0104]
[Table 2]

[0105]
[Table 3]

[0106]
[Table 4]

[0107]
[Table 5]

[0108]
[Table 6]

[0109]
[Table 7]

[Brief description of the drawings]
[0110]
FIG. 1 is a first process pattern diagram schematically showing the processing content of each process.
FIG. 2 is a second process pattern diagram schematically showing the processing content of each process.
FIG. 3 is a third process pattern diagram schematically showing the processing content of each process.
FIG. 4 is a fourth process pattern diagram schematically showing the processing content of each process.
FIG. 5 is a fifth process pattern diagram schematically showing the processing content of each process.
FIG. 6 is a sixth process pattern diagram schematically showing the processing content of each process.
FIG. 7 is a seventh process pattern diagram schematically showing the processing content of each process.
FIG. 8 is an eighth process pattern diagram schematically showing the processing content of each process.
FIG. 9 is a ninth process pattern diagram schematically showing the processing content of each process.

Claims (7)

An RFeB-based alloy containing, as main components, a rare earth element (hereinafter referred to as “R”) containing yttrium (Y), boron (B), and iron (Fe), has a predetermined hydrogen pressure of 10 to 100 kPa. A high-temperature hydrogenation step of maintaining a processing atmosphere at a predetermined first processing temperature (hereinafter referred to as “T1”) in 953 to 1133K at one processing pressure (hereinafter referred to as “P1”);
The RFeB-based alloy after the high-temperature hydrogenation step is subjected to a second processing temperature (hereinafter referred to as “T2”) at a second processing pressure (hereinafter referred to as “P2”) having a hydrogen partial pressure of 10 kPa or more and a temperature of 1033 to 1213 K. called.), and and a tissue stabilization process of holding the processing atmosphere satisfying the condition of T2> T1 or P2> P1,
The RFeB-based alloy after the structure stabilization step is a third treatment pressure (hereinafter referred to as “P3”) with a hydrogen partial pressure of 0.1 to 10 kPa , P3 <P2, and a temperature of 1033 to 1213 K. A controlled exhaust process for maintaining a processing atmosphere at a third processing temperature (hereinafter referred to as “T3”),
A forced exhaust process for removing residual hydrogen (H) from the RFeB-based alloy after the controlled exhaust process;
A method for producing anisotropic magnet powder, comprising: An RFeB-based alloy containing, as main components, a rare earth element (hereinafter referred to as “R”) containing yttrium (Y), boron (B), and iron (Fe), has a predetermined hydrogen pressure of 10 to 100 kPa. A high-temperature hydrogenation step of maintaining a processing atmosphere at a predetermined first processing temperature (hereinafter referred to as “T1”) in 953 to 1133K at one processing pressure (hereinafter referred to as “P1”);
  The RFeB-based alloy after the high-temperature hydrogenation step is subjected to a second processing temperature (hereinafter referred to as “T2”) at a second processing pressure (hereinafter referred to as “P2”) having a hydrogen partial pressure of 10 kPa or more and a temperature of 1033 to 1213 K. And a tissue stabilization step of maintaining a processing atmosphere satisfying the conditions of P2 ≧ P1, T2> T1 or P2> P1, T2 ≧ T1,
  The RFeB-based alloy after the structure stabilization step is a third treatment pressure (hereinafter referred to as “P3”) with a hydrogen partial pressure of 0.1 to 10 kPa, P3 <P2, and a temperature of 1033 to 1213 K. A controlled exhaust process for maintaining a processing atmosphere at a third processing temperature (hereinafter referred to as “T3”),
  A forced exhaust process for removing residual hydrogen (H) from the RFeB-based alloy after the controlled exhaust process;
  A method for producing anisotropic magnet powder, comprising: Said tissue stabilizing process, a manufacturing method of an anisotropic magnet powder as claimed in claim 1 or 2 is a step to 200kPa an upper limit of said P2. Furthermore, the manufacturing method of the anisotropic magnet powder of Claim 1 or 2 provided with the cooling process which cools the said RFeB type alloy after the said control exhaust process and before the said forced exhaust process. Furthermore, the manufacturing method of the anisotropic magnet powder of Claim 1 or 2 provided with the low temperature hydrogenation process of hold | maintaining the said RFeB type alloy in the hydrogen atmosphere whose temperature is 873K or less before the said high temperature hydrogenation process. Furthermore, after the controlled exhaust process or the forced exhaust process, an RFeB-based alloy obtained by adding dysprosium (Dy), terbium (Tb), neodymium (Nd), praseodymium (Pr) or lanthanum (La) , Referred to as “R1”), a mixing step of mixing a diffusing material containing at least one or more into a mixed powder;
A diffusion heat treatment step of heating the mixed powder and diffusing the R1 into and on the surface of the RFeB-based alloy;
The manufacturing method of the anisotropic magnet powder of Claim 1 or 2 provided with these.   The anisotropic magnet powder according to claim 6, further comprising a dehydrogenation step of removing the hydrogen from the mixed powder before the diffusion heat treatment step when hydrogen remains in the mixed powder after the mixing step. Production method.

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